Tomáš Vymazal

Determination and evaluation of the air permeability coefficient using Torrent Permeability Tester

A quality of a covercrete (covercrete = cover concrete) up to a depth of 20–50 mm practically decides about the durability of concrete of a structure. The covercrete prevents accessing of acid substances from the atmosphere to steel reinforcement. For evaluation of a state of the covercrete from the durability viewpoint is possible to use a relatively new NDT method for determination of concrete air permeability. The work of the team focuses on the determination of the quality of the surface layer of concrete using the TPT method and specification of the impact of humidity on the value of the air permeability coefficient.

The Effect of Concrete Quality on the Acoustic Emission Parameters during Three-Point Bending Fracture Test

Acoustic emission is an experimental tool well suited for monitoring fracture processes. The paper presents experiment focused on analysing acoustic emission signals captured during three-point bending fracture test of specimens of concrete. Quantitative acoustic emission techniques were used to measure micro fracture properties. For three different concrete mixtures typical acoustic emission patterns were identified in the acoustic emission records to further describe the under-the-stress behaviour and failure development. If we have a better understanding of the relationships between micro structural events and macroscopic behaviour we can better formulate predictive models for large-scale structural performance and reliability. An understanding of microstructureperformance relationships is the key to true understanding of material behaviours. Three-point bending fracture tests were conducted on these specimens and load versus crack mouth opening displacement (Load-CMOD) diagrams were recorded during the testing.

Repeatability and Reproductibility of Results of Fresh Concrete Testing

The aim of this paper is to summarize the results of 11 experiments which focused on assessing the precision of results of fresh concrete testing. The observed characteristics are slump test, flow table test, density and air content. More than twenty participants (testing laboratories) took part in these experiments. The test results were evaluated with statistical methods used for evaluations of interlaboratory comparisons. The article deals especially with the values of repeatability and reproducibility, which provide further understanding of the interval within which it is possible to expect with the given probability the test results measured in one or more laboratories.

Repeatability and Reproducibility of the Static Elastic Modulus of Concrete Measurement

In recent years, the static modulus of elasticity is one of the most discussed property of hardened concrete. The aim of this article is to show results of 6 performed experiments focused on test results precision. The measurements were made according to the standards ISO 6784 and ISO 1920-10. More than 20 participants (laboratories) from Europe took part in these experiments. Test results were compared using the statistical methods for interlaboratory comparison. Repeatability and reproducibility, which provide more detailed information about range of expected values of elastic modulus, are the most discussed characteristics in the article.

Introduction to an Approach to Performing Sustainability Quantification of Concrete Structures

Efficient sustainability management requires the use of tools that enable the quantification, measurement or comparison of material, technological and construction variants. Tools of this kind which have been developed around the world in recent years include various indicators, indexes, etc. Generally, technical, economic, ecological and socio-cultural areas must all be included. Such a tool can be used as a powerful marketing aid and as support for the transition to the “circular economy”. Life Cycle Assessment (LCA) procedures are also used, alongside other approaches. LCA is a method that evaluates the life cycle of a structure from the point of view of its effect on the environment. Processes starting with the mining of mineral resources and including their transport, production and use up to their final processing as waste (recycling) are all taken into account. In addition, consideration is given to energy and raw material costs, and to environmental impact throughout the whole life cycle – e.g. through emissions. The presented contribution focuses on the quantification of sustainability connected with the use of various types of concrete with regard to their resistance against the effect of degrading influences. Sustainability factors are also determined using information regarding service life and “eco-costs”. The aim is to present a suitable methodology which can simplify decision-making concerning the design and choice of concrete mixes from a wider perspective, i.e. not only from the aspects of load-bearing capacity or durability.

Influence of Coarse Aggregate Grain Size on Frost Resistance of Concrete

This paper deals with the influence of the coarse aggregate grain size on the frost resistance of concrete. For the purpose of the experiment, three types of concrete were produced, varying only in the maximum grain size of the used natural aggregate. The evaluation of the frost resistance of concrete is based on non-destructive (NDT) dynamic and static testing methods. The results of the experiment indicate influences of the aggregate used in the production of the concrete on the results of its frost resistance.

Three-Point Bending Test Evaluation of Concrete Specimens by Non-Traditional Analysis of Acoustic Emission Method

The aim of the paper is focused on the analysis of the mechanical properties of the concrete specimens with plasticizer at three point bending test by the signal analysis of the acoustic emission signal. The evaluations were compared the measurement and the results obtained with theoretical presumptions. The Joint Time Frequency Analysis applied on measurement data and its evaluation is described. It is well known that the Acoustic Emission Method is a very sensitive method to determine active cracks into structure. However, evaluation of acoustic emission signals is very difficult. A non-traditional method was used to signal analysis of burst acoustic emission signals recorded during three point bending test.